The present invention relates to a method of erasing information on a semiconductor component comprising a plurality of non-volatile memory elements by irradiating same with erasing radiation which penetrates the semiconductor component. Additionally, the present invention relates to a device for erasing information on an electronic semiconductor component comprising a plurality of non-volatile memory elements with irradiating means configured to expose the semiconductor component to erasing radiation, wherein the invention particularly relates to a method and a device for completely and permanently destroying information stored on data carriers by means of directly or indirectly ionizing radiation.
A plurality of data and files, such as, for example, secret documents, personal data, sensitive company data etc., is to be erased reliably or destroyed after expiry of retention periods or before disposing of the data carriers so as to satisfy legal obligations or prevent undesired spreading of the data.
Apart from a frequently insufficient erasure of information or data by means of software, there are three methods which are applied commercially for securely destroying electronically stored information and data. Apart from the so-called degaussing of magnetic data carriers and thermal destruction of the information or data by exceeding the Curie temperature of the data carrier, up to now the only possibility available for electronic memory of class E pursuant to DIN 66399 is mechanically crushing the data carriers. Variations of mechanical crushing differ, as regards different security stages, in the size of the particles produced by crushing.
Three stages of cleaning a data carrier and, consequently, erasing or destroying the information and data on the data carrier may be differentiated between. With logic cleaning, a first stage, the data, after cleaning, may no longer be accessed via standard interfaces of the data carrier. With digital cleaning, a second stage, accessing the data in any digital form is prevented after cleaning, even when bypassing the standard interfaces. With analog cleaning, a third stage, the analog signal which physically encodes the data is degraded, after cleaning, to such an extent that it may no longer be read, even when using the most advanced analog methods.
These three stages, in the order of logic cleaning, digital cleaning and analog cleaning, stand for an increasing erasing security for the data or data carriers from unauthorized access. With magnetic hard disk drives, the three stages may be represented as follows. Logically cleaning, meaning erasing the file, results in the file to be removed from the file allocation table (FAT) of the hard disk drive, wherein, however, the file itself is still present on the hard disk drive. Accessing the file by simply calling the file is prevented due to the erased entry in the FAT, the standard interface. Digital cleaning by overwriting the file to be erased results in renewed magnetization of the hard disk drive, wherein traces of the original magnetization may still be present. Analog cleaning means completely destroying the magnetization of the hard disk drive by means of a strong external magnetic field by means of degaussing or by exceeding the Curie temperature by heating up the hard disk drive. Alternatively, nearly analog cleaning may also be done by mechanical crushing. The number of bits which may potentially be restored or read out per particle are dependent on the size of the particles obtained when mechanically crushing and the physical dimension of the bit on the data memory.
Flash-based, non-volatile memories, such as, for example, flash electrically erasable programmable read-only memories (EEPROMs), are increasing in importance, either as a USB stick or memory card, as built-in permanent memory in smartphones or tablet PCs, or as a substitute for magnetic hard disk drives in the form of solid-state drives (SSDs). Non-volatile memories necessitate reliably methods for destroying sensitive data. There are approved and verified standards for optical and magnetic media. With electronic memories, for example flash memories, only mechanical crushing of the data carrier is known in order to achieve analog cleaning.
Flash memories are the most widespread type of non-volatile memories which are based on the principle of storing information by means of floating gates (FG). There are basically two different addressing technologies for flash memories: NOR and NAND. With NOR flash memories, directly writing on or reading from individual memory cells is possible. Thus, it is possible directly to call programs from an NOR flash memory. Erasing and programming the memory, however, are very slow, wherein the memories survive only about 10% of writing/reading cycles of an NAND memory with regard to lifetime before they become useless. A typical field of application for NOR flash memories is storing firmware.
In NAND flash memories, several cells are connected in series to form a PAGE, similar to an NAND gate, where the name comes from. The cells of a PAGE may then be read and written to only together. NAND memories generally exhibit a higher cell density and allow faster programming of the cells and a higher number of writing and reading cycles within their lifetime, as compared to NOR memories. NAND memories are used for mass storage and from an economic point of view, at present are the fastest growing technology. It is common to all flash memories that erasing memory cells and, thus, data at the same time is possible only for a larger block of memory cells.
Securely destroying data by overwriting is not possible, since in NAND flash memories, as are primarily used for mass storage, writing and, thus, programming a memory cell from state 1 to state 0 are possible only page-wise and erasing by offsetting the bits of the memory elements stored in the non-volatile memory elements from the logic state 0 to state 1 possible only in blocks, i.e. for a block of memory elements. Changes in the data usually are not done by overwriting the physical memory cells, but by means of writing the data to a different location of the data storage and by releasing the original location of the data storage. The data to be erased remain on the memory. The controllers of the data memory may advantageously use locations for writing new data which up to then were empty in order to compensate the disadvantage of finite ways of writing in the flash memory. This results in a reduced effectivity of erasing memory by means of overwriting. There may be regions on the data storage which are available only to the controller of the data storage for optimization purposes, but are inaccessible for the user. The result here is that the only way known so far or discussed for analog cleaning of electronic memories is mechanically crushing the data storage.
A way of cleaning electronic memory media from sensitive data most effectively, i.e. reliably and in an uncomplicated manner, would consequently be desirable.